氮掺杂钙钛矿复合氧化物的合成与催化性能

重庆大学本科学生毕业设计（论文）氮掺杂钙钛矿复合氧化物的合成及催化性能学生：李涯皓学号：20076857指导教师：高文亮副教授专业：材料化学重庆大学化学化工学院二O一一年六月GraduationDesign(Thesis)ofChongqingUniversityStudyonSynthesisandPhotocatalyticPerformanceofN-dopedperovskiteoxidesStudyUndergraduate:LiYahaoSupervisor:Prof.GaoWenliangMajor:MaterialChemistryChemistryandChemicalEngineeringCollegeChongqingUniversityJune2011重庆大学本科学生毕业设计（论文）中文摘要I摘要随着全球环境问题和能源问题的不断加剧，以及对清洁能源和可再生能源的开发的迫切需要，使得对太阳能的利用备受关注。其中，能够有效利用太阳能的可见光光催化剂成为了研究热点。钙钛矿型复合氧化物由其高光催化活性、高稳定性及高环境友好性而被视为研发可见光光催化剂的重要材料。而对钙钛矿氧化物进行氮掺杂，在O位掺入N离子，能够有效的减小其禁带宽度，进而延展其光响应域至可见光区，使其获得可见光光催化活性。本论文通过溶胶-凝胶法合成了钙钛矿型复合氧化物Nd1-xSrxMnO3，通过其对甲基橙在紫外光照射下的光催化降解研究催化剂组成及溶液条件对催化活性的影响，随后在通入NH3、不同温度条件下通过高温焙烧法对Nd1-xSrxMnO3进行了氮掺杂，并研究了其可见光催化性能并对其进行了贵金属改性。结果表明，Nd1-xSrxMnO3复合氧化物在紫外光照射下具有一定的光催化活性，并且其催化活性随着Sr掺杂量的提高而提高。但NdMnO3的钙钛矿型结构会随着Sr掺杂量的提高而逐渐被破坏。与此同时，当溶液pH=2时，催化剂达到其最大光催化活性。故Nd0.7Sr0.3MnO3在保有钙钛矿结构的同时具有最高的催化活性。其在pH=2，光照30min的条件下对40ppm的甲基橙溶液的催化降解率达到了80.3%。在500℃下进行氮掺杂的N-Nd0.7Sr0.3MnO3复合氧化物具有最高的可见光催化活性，pH=2，可见光光照30min的条件下，对40ppm的甲基橙溶液的催化降解率达到了79.4%，成功的获得可见光光催化剂。进一步对其进行贵金属Ag负载后，催化剂在苯乙烯氧化体系中获得了较高的苯乙烯转化率及环氧苯乙烷选择性，当负载比达到4%时，苯乙烯的转化率和环氧苯乙烷的选择性达到最高，分别为26.4%和61.2%。关键词：溶胶-凝胶法，钙钛矿，氮掺杂，可见光光催化，苯乙烯环氧化重庆大学本科学生毕业设计（论文）ABSRACTIIAbstractWiththeglobalenvironmentalproblemsandtheenergyproblemsincreased,aswellastheeagerneedsofthecleanandreproducibleenergyoftheworld,theuseofthesolarenergyattractedmanypeople’sattention.Withinthem,thevisible-lightresponsesPhotocatalystswhichcanusethesolarenergyeffectivelybecometheresearchhotspot.Thehighphotoactivity,highstabilityandhighenvironmentalfriendlinessofPerovskiteoxidesmakeittobeoneofthepromisingmaterialsofdevelopingvisible-lightresponsePhotocatalysts.Andafternitrogen(N)doping,mixingNionintooxygen(O)position,onecaneffectivelydecreasethelengthofperovskiteoxide’sbandgap,itmeansthegreatenofitslightrespondarea,thusmakesitbecomevisible-lightsensitivephotocatalysts.ThisarticlepreparedperovskitetypeoxidesNd1-xSrxMnO3viasol-galmethod,andthenweresearchedtherelationshipbetweenitscomponentandthesolventconditionswithitsphotocatalyticactivitythroughthedegradationofMethylorange,whichaddedthecatalyst,underultravioletirradiation.AfternitrogendopingtothecatalystviacalcinationsatdifferenttemperatureinNH3atmosphere,weexploreditsphotocatalyticactivityandthenmadepreciousmetalsModificationtowardsit.TheresultshowsthatperovskitetypephotocatalystNd1-xSrxMnO3haveobviousphotoactivityunderultravioletirradiationandwiththeincreasedofSrexistedinthecompound,itsactivityincreased.However,addingSrintotheoxidewillchangeitsstructure.AndunderpH2,thecatalystgainsthehighestphotoactivity.ThusNd0.7Sr0.3MnO3hasthehighestactivitywhileremainitsperovskitestructure.Thedegradationof40ppmMethylorangeatpH2reached80.3%afterultravioletirradiationfor30min.TheN-dopingNd0.7Sr0.3MnO3whichcalcinedat500℃hasthehighestvisible-lightphotoactivity.Thedegradationof40ppmMethylorangeatpH2reached79.4%aftervisible-lightirradiationfor30min.Wehavesuccessfullydevelopedavisible-lightresponsesphotocatalyst.Moreover,thecatalystgainsHighstyreneconversionandselectivityofstyreneoxideinstyreneoxidationsystemafterloadedwithAg.Whentheloadratioreaches4%,thestyreneconversionandselectivityofstyreneoxidereachedthetop,are26.4%and61.2%respectively.Keywords：Sol-gel,Perovskite,N-doping,Visible-lightPhotocatalysts,Styreneepoxidation.重庆大学本科学生毕业设计（论文）目录III目录摘要.......................................................................IAbstract.....................................................................II1绪论...................................................................11.1钙钛矿复合氧化物的结构特征...........................................11.1.1理想的钙钛矿结构...............................................11.1.2类钙钛矿结构...................................................21.2钙钛矿复合氧化物的应用...............................................31.3光催化简介...........................................................31.3.1光催化研究背景和现状...........................................31.3.2半导体光催化机理...............................................41.3.3光催化材料的发展...............................................51.4影响ABO3型复合氧化物光催化活性的因素.................................61.4.1B位离子.......................................................61.4.2A位离子.......................................................71.4.3掺杂...........................................................71.4.4粒径...........................................................81.5钙钛矿型复合氧化物的制备方法.........................................91.5.1高温固相法.....................................................91.5.2溶胶-凝胶法....................................................91.5.3共沉淀法......................................................101.5.4水热法........................................................101.5.5燃烧法........................................................101.5.6机械混合法....................................................101.6氮掺杂对钙钛矿型氧化物的催化性能影响................................111.6.1氮掺杂可见光响应的机理........................................111.6.2对氮掺杂化合物催化性能的改进..................................111.7苯乙烯环氧化.....................................................